Luck in the Shadows by Lynn Flewelling 

When young Alec of Kerry is taken prisoner for a crime he didn’t commit, he is certain that his life is at an end. But one thing he never expected was his cellmate. Spy, rogue, thief, and noble, Seregil of Rhiminee is many things–none of them predictable. And when he offers to take on Alec as his apprentice, things may never be the same for either of them. Soon Alec is travelling roads he never knew existed, toward a war he never suspected was brewing. Before long he and Seregil are embroiled in a sinister plot that runs deeper than either can imagine, and that… Read more.